This used to happen all the time back when Twitter was a baby, but the fact that the service is down - at least for some and going on 30-40 minutes now - has become rare enough to be noteworthy.
The service-monitoring site Down Right Now lists the problem as a "likely service disruption."
Twitter's status blog has no news yet.
On the bright side? No professional athlete has embarrassed himself for the past 30 minutes ... at least on Twitter.
(Update, 10 a.m.: It would appear the service disruption is not total, as longtime Network World contributor Dave Kearns tells me via Facebook: "I get that (message) from twitter.com, but my tweetstream reader (Janetter) is having no problems at all, either reading or writing.")
(Update 2, 10:20 a.m.: It's definitely a localized issue. Twitter's support account reports: "Some users are currently unable to log in to their accounts. We are aware of this issue and our engineers are working to fix it.")
(Update 3, 11:30 a.m.: All fixed now, at least for me.)
Sign up for CIO Asia eNewsletters.